In LTE (Long Term Evolution) systems specified by the 3GPP (3rd Generation Partnership Project), in order to actualize faster transmission, MIMO (Multiple Input Multiple Output) transmission is adopted in which a radio base station apparatus uses a plurality of reception antennas. By using this MIMO transmission, it is possible to perform scheduling in the spatial domain, in addition to scheduling in the time domain and frequency domain. As MIMO transmission, there are single user MIMO (SU-MIMO) in which a radio base station apparatus having a plurality of antennas parallel transmits a plurality of signals to a single user (mobile terminal apparatus), and multi-user MIMO in which a radio base station apparatus having a plurality of antennas performs spatial multiplexing to transmit to a plurality of users (mobile terminal apparatuses) (SDMA: Space Division Multiple Access). In this MIMO transmission, a PMI (Precoder Matrix Indicator) indicative of a transmission weight for each antenna is used in downlink transmission.
In LTE systems, scheduling in the time domain, frequency domain and spatial domain is dependent on channel states in downlink. Therefore, for scheduling in the time domain, frequency domain and spatial domain in the radio base station apparatus, mobile terminal apparatuses report channel states. As a parameter to report the channel state, there are the above-mentioned PMI, and downlink quality information (CQI: Channel Quality Indicator) used in adaptive modulation/demodulation and coding processing (AMC: Adaptive Modulation and Coding scheme). By transmitting such PMI and CQI (Channel State Information: CSI or feedback information) to the radio base station apparatus as feedback, the radio base station apparatus performs scheduling in the time domain, frequency domain and spatial domain.